Parking assistance system for vehicles and corresponding method

ABSTRACT

The invention relates to a method for operating a parking assistance system for a vehicle, comprising at least one distance sensor that detects at least sections of the lateral immediate vicinity of the vehicle and at least one path sensor that detects the path travelled by the vehicle. According to the method, a control device determines the length and/or width of a parking space from the values measured by the sensors as the vehicle drives past said parking space. The invention is characterised in that the measured length and/or width of the parking space is/are corrected by a correction value and/or that depending on the speed of the vehicle as it drives past the parking space, the measurement is taken by means of the distance sensor at different time intervals.

This application is the national stage of PCT/EP03/01111 filed on Feb.05, 2003 and also claims Paris Convention priority of DE 102 16 346.4filed on Apr. 13, 2002.

BACKGROUND OF THE INVENTION

The invention concerns a method for operating a parking assistancesystem for a vehicle, with at least one distance sensor which probes atleast regions which are laterally proximate to the vehicle, and with atleast one path sensor which detects the path travelled by the vehicle,wherein a control device determines the length and/or width of theparking space from the values of the distance sensor and the path sensorwhich are detected while passing the parking space. The invention alsoconcerns a parking assistance system and a vehicle.

DE 297 18 862 U1 discloses parking assistance systems of this type. Ithas turned out that the measured size of the parking space differs fromthe actual size of the parking space.

It is therefore the underlying object of the invention to furtherdevelop a method of the above-mentioned type such that the size of theparking space is determined with maximum accuracy when passing theparking space.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention with a methodof the above-mentioned type in that the length and/or width of theparking space which is determined in a conventional method is correctedby a correction value in dependence on the lateral distance between thevehicle and the objects bordering the parking space, e.g. two parkingvehicles. It has turned out that, due to the non-linear geometry of theradiation lobe of the distance sensor, the actual length of the parkingspace is not determined, rather a length from the point in time when oneparked vehicle leaves the distance sensor lobe to the point in time whenthe other parked vehicle enters the lobe of the distance sensor. Themeasuring result is therefore falsified by half the diameter of the lobewhen the object exits as well as enters the lobe. For non-cylindricallobes and different lateral distances from the objects delimiting theparking space, different lengths are measured for the same parkingspace. In accordance with the invention, correction of the measuredlength of the parking space with a correction value advantageouslycompletely eliminates the inaccuracy resulting from the radiation lobespecific to the distance sensor.

In accordance with the invention, alternatively or additionally, themeasurement is carried out by the distance sensor at different timeintervals in dependence on the speed of the vehicle while passing theparking space. To determine the size of the parking space with maximumaccuracy, measurement at slow speeds e.g. is carried out in relativelyshort time intervals. To obtain a first impression of the size of theparking space, measurement while passing the parking space at a higherspeed, can be carried out at relatively long time intervals to minimize,in particular, calculation effort, which is then available for othervehicle systems.

The correction value for non-cylindrical radiation lobes preferablydepends on the lateral distance between the vehicle and the objectsdelimiting the parking space. Different correction values are used independence on the lateral distance from the objects.

In a preferred embodiment of the invention, the correction value dependson the geometry of the distance sensor lobe. When the geometry of thelobe of the distance sensor is known, the correction value can bedetermined in a simple fashion in dependence on the distance of therespectively detected object.

In accordance with the invention, the correction value depends linearlyon the radial distance between the main radiation direction (thelongitudinal axis of the lobe) and the surface of the lobe in the planewhere the object delimiting the parking space enters or exits the lobe.The correction value preferably corresponds to the radial distancebetween the main radiation direction and the point where the respectiveobject exits or enters the lobe.

In an advantageous embodiment of the invention, the correction value hasdifferent fixed values in different distance ranges from the objectsdelimiting the parking space. This is advantageous in that calculationeffort can be reduced by providing the fixed values.

It is thereby feasible that a first distance range is in the regionbetween 0 and 1 m from the objects delimiting the parking space. Thecorrection value provided as a fixed value may then e.g. be 0.5 m.

A further distance range may comprise e.g. the distance region between 1m and 1.2 m between the vehicle and the objects delimiting the parkingspace. In this case, a fixed correction value may be 0.2 m.

It is also feasible in accordance with the invention that the correctionvalue is 0 when the distance range or the lateral distance between thevehicle and the objects delimiting the parking space is larger than 1.2m.

When the vehicle travels at a speed of more than 19 km/h, distancesensor measurements are preferably carried out by the distance sensor attime intervals of 20 ms. If the speed of the vehicle is between 10 km/hand 19 km/h, the distance sensor measurement is preferably carried outin time intervals of 40 ms. If the vehicle speed is less than 10 km/h,the measurement is preferably carried out every 100 ms. This produces avery precise measurement at slow vehicle speeds, i.e. during deliberateparking intent.

The distance sensor may e.g. be an ultrasonic sensor, an infraredsensor, a radar sensor or an optical sensor. The path sensor candetermine the travelled path using ABS signals, transmission signals,speedometer signals or the like. It may also be part of an ABS system, atransmission system, a speedometer system or the like. This isadvantageous in that components which already exist in the vehicle canbe used as path sensors.

Means for quantitative and/or qualitative information are provided toinform the driver whether the parking space just passed is large enoughfor the vehicle. Such means may be display systems or loudspeakersystems.

In a further preferred embodiment of the invention, the distance sensorcan be operated in different modi, in particular, as a sensor for aninventive parking assistance system and as a parking assistance systemto prevent collisions during parking. This is advantageous in that thesame sensor may be used for different functions.

The above-mentioned object is also achieved by a parking assistancesystem for carrying out the inventive method. A vehicle comprising sucha system, also achieves the above-mentioned object.

BRIEF DESCRIPTION OF THE DRAWING

Further advantageous embodiments and details of the invention can beextracted from the following description which explains the inventionwith reference to the embodiments shown in the drawing.

FIG. 1 shows a vehicle with an inventive parking assistance systembefore passing a parking space;

FIG. 2 shows a vehicle with an inventive parking assistance system;

FIG. 3 shows the front section of the vehicle in accordance with FIG. 2while passing a parking space;

FIG. 4 shows a flow chart of an inventive parking assistance system; and

FIGS. 5 a and 5 b show a vehicle, wherein the inventive parkingassistance system is operated in two different modi.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a vehicle 10 which moves in the travel direction F andpasses a parked vehicle 12. There is a parking space 16 between afurther vehicle 14 and the vehicle 12. The parking space 16 has anactual length l. The vehicle 10 (shown in an enlarged scale in FIG. 2)has one distance sensor 18 at each longitudinal side of the vehicle. Thedistance sensor 18 detects the lateral proximity of the vehicle. Theregions detected by the sensors 18, so-called lobes, are characterizedin the figures by reference numeral 20.

The vehicle 10 also has a path sensor 22 which is coupled e.g. to theABS system, the transmission or the speedometer of the vehicle 10. Thevehicle 10 also comprises a control device 24 which is coupled via lines26 to the distance sensors 18 and the path sensor 22. The control device24 can determine the length l of the parking space 16 from the distancesensors 18 and the path sensor 22 (see description FIG. 3). The vehicle10 also has a display 28 connected to the control device 24, which givesthe driver information about the size of the parking space 16 afterpassing by the parking space 16.

In addition to the path sensor 22, the vehicle 10 also has a speedsensor 30 which is coupled to the control device 24. Further distancesensors 32 are provided in the front and rear part of the vehicle, whichare part of parking assistance system to warn the driver of collisionswith objects present in the proximity of the vehicle when a safetydistance has been surpassed.

FIG. 3 explains the inventive parking assistance system. The vehicle 10is shown in two positions, t₁ and t₂, at different points in time. Thetwo objects 12 and 14 which delimit the parking space are not aligned,rather slightly mutually offset. The object 14 is therefore closer tothe passing vehicle than is the object 12.

Prior to time t₁, the distance sensor 18 measures the lateral distancex₁ from the parked vehicle 12. At the time t₁, the corner region 34 ofthe vehicle 12 leaves the lobe 20 of the distance sensor 18. Thedistance sensor 18 consequently informs the control device 24 that theparking space 16 starts at t₁. At this time t₁, the path sensor 22starts to measure the path travelled up to time t₂, at which point intime t₂, the corner region 36 of the vehicle 14 enters the lobe 20 ofthe distance sensor 18. The control device 24 therefore receives theinformation that the end of the parking space 16 is reached. The lengthl′ is measured as the length of the parking space 16 via the pathtravelled between the two times t₁ and t₂.

As is clearly shown in FIG. 3, the length l′ does not correspond to theactual length l of the parking space 16.

In accordance with the invention, a correction value k is added to thevalue l′ in order to obtain the actual length l of the parking space 16from the length l′. In accordance with the embodiment of FIG. 3, thecorrection value is k=d₁+d₂. The length l of the parking space 16 iscalculated as follows: l=l′+(d₁+d₂).

The values d₁ and d₂ can be determined e.g. as follows: The distance x₁of the passing vehicle 10 from the vehicle 12 is determined. Thegeometry of the lobe surface of the lobe 20 is known. From x₁, thedistance d₁ can be determined, which corresponds to the radial distancefrom the main radiation direction 38 to the corner region 34 of thevehicle 12. A similar evaluation obtains for the distance d₂. At timet₂, d₂ equals the radial distance from the main radiation direction 38to the corner region 36 of the vehicle 14.

Due to the fact that the vehicles 12 and 14 are parked such that theyare mutually offset, d₁ and d₂ differ. If the vehicles 12 and 14 arecoplanar, the values d₁ and value d₂ are equal.

The values d₁ and d₂ can also be estimated. In accordance with theinvention, the lateral distance between the vehicles 10 and the vehicles12 and 14 delimiting the parking space can be separated into threedistance ranges. A first distance range extends from 0 to 1 m, a seconddistance range extends from 1 m to 1.2 m, and a third distance rangecomprises distances of more than 1.2 m. If the vehicles 12 and 14 are inthe first distance range, a general correction value of approximately0.5 m may be provided, which includes the two values d₁ and d₂. If thelateral distance between the vehicle 10 and the vehicles 12 and 14 isbetween 1 m and 1.2 m, a general correction value may be 0.2 m. If thecorresponding distance is more than 1.2 m, the correction value may be0.

FIG. 4 schematically shows the inventive method for operating theparking assistance system. The distance sensor 18 measures the lateraldistance between the vehicle 10 and the objects 12, 14 present in thelobe 20. This value x is communicated to the control device 24. If x iscorrespondingly large, i.e. if a parking space is detected, the pathsensor 22 or the speed sensor 30 measures the path or the speed of thevehicle until the distance sensor 18 detects an object 14. Themeasurement produces a length l′ of the parking space. l′ is thereby afunction of the path s travelled and of the detected distance x, or afunction of the travelled speed and the detected distance x, i.e.:l′=f(s,x) or l′=f(v,x). To obtain the actual length l of the parkingspace, the value l′ is corrected with a correction value k. Thecorrection value k is thereby a function of the distance x from theobjects 12, 14 delimiting the parking space 16, i.e. k=f(x). The actuallength l of the parking space is calculated as follows: l=l′+k. Thislength l is displayed to the driver, in a qualitative or quantitativefashion, via display 38.

To ensure exact measurement of the parking space 16, the measurement iscarried out by means of the distance sensor 18 at different timeintervals depending on the speed v of the vehicle 10 during passage bythe parking space 16. The measuring frequency ƒ is consequently afunction of the speed v of the vehicle 10, i.e. ƒ=f(v). If the vehiclespeed is more than 19 km/h, the measurement can be carried out e.g.every 20 ms. If the vehicle speed is between 10 km/h and 19 km/h, timeintervals of 40 ms are favorable. In a particularly advantageousfashion, time intervals of 100 ms for distance sensor 18 measurementsare favorable when the vehicle speed is less than 10 km/h.

FIG. 5 a shows the vehicle 10, wherein the distance sensors 18 are partof an inventive parking assistance system to determine the size of aparking space. The distance sensors 18 can, however, also be part of aparking assistance system to prevent collisions during parking (see FIG.5 b). The distance sensors 18 are thereby operated in another modus,e.g. the control device 24 is operated using other appropriate softwareto detect the proximity 20′. The distance sensors 32 detect the regions40. This is advantageous in that the distance sensors 18 can be used fordifferent tasks without requiring additional components.

Changing operation of the sensors 18 between the two modi isadvantageous. The alternating frequency may be relatively high such thata suitable parking space is searched and collision with an objectreaching proximity is prevented.

All features shown in the description, the following claims and thedrawings, may be essential to the invention individual or collectivelyin arbitrary combination.

1. A method for operating a parking assistance system for a vehicle, themethod comprising the steps of: a) moving the vehicle past a parkingspace; b) measuring, during step a), distances within a lateral regionproximate the vehicle using at least one distance sensor; c) measuring,during step a), a path length travelled by the vehicle using at leastone path sensor; d) determining at least one of a length and width ofthe parking space using results of steps b) and c); and e) correctingthe results of step d) by a correction value which is dependent on themeasurements of at least one of step b) and step c), step b) beingrepeatedly carried out as the vehicle passes by the parking space,wherein a time interval between successive executions of step b) isdecreased in response to an increase in the speed of the vehicle.
 2. Themethod of claim 1, wherein said correction value depends on a lateraldistance between the vehicle and objects delimiting the parking space.3. The method of claim 2, wherein said distance sensor hasnon-cylindrical radiation lobes.
 4. The method of claim 1, wherein saidcorrection value depends on a geometry of a lobe of said distancesensor.
 5. The method of claim 1, wherein said correction value dependslinearly on a radial distance between a main radiation direction and asurface of a lobe of the distance sensor at a point of exit and entry ofan object delimiting the parking space into and out of the lobe.
 6. Themethod of claim 1, wherein said correction value is a constant value fora given range of distances from objects delimiting the parking space. 7.The method of claim 6, wherein said correction value is 0.5 m when alateral distance between the vehicle and objects delimiting the parkingspace is less than 1 m.
 8. The method of claim 1, wherein saidcorrection value is 0.2 m when a lateral distance between the vehicleand objects delimiting the parking space is between 1 m and 1.2 m. 9.The method of claim 1, wherein said correction value is zero when alateral distance between the vehicle and objects delimiting the parkingspace is more than 1.2 m.
 10. The method of claim 1, wherein step b) iscarried out by said distance sensor at time intervals of 20 ms when avehicle speed is more than 19 km/h.
 11. The method of claim 1, whereinstep b) is carried out by said distance sensor at time intervals of 40ms when a vehicle speed is between 10 km/h and 19 km/h.
 12. The methodof claim 1, wherein step b) is carried out by said distance sensor attime intervals of 100 ms when a vehicle speed is less than 10 km/h. 13.The method of claim 1, wherein said distance sensor is at least one ofan ultrasonic sensor, an infrared sensor, a radar sensor, and an opticalsensor.
 14. The method of claim 1, wherein said path sensor receivesinput values as at least one of ABS signals, transmission signals, andspeedometer signals.
 15. The method of claim 1, wherein said path sensoris part of one of an ABS system, a transmission system, and aspeedometer system.
 16. The method of claim 1, further comprising meansfor quantitative or qualitative communication to a driver as to whetheror not parking of the vehicle into the parking space is possible. 17.The method of claim 1, wherein said distance sensor is operated indifferent modi.
 18. The method of claim 17, wherein said distance sensoris operated to prevent collisions during parking.
 19. A parkingassistance system for carrying out the method of claim
 1. 20. A vehiclecomprising the parking assistance system of claim 19.